The first-ever fest is bringing together some 20 such works over the course of four very busy days today through Sunday, at sites mostly in and around the joint Playhouse/UC San Diego Theatre District.

The event includes productions going up not only in autos (“The Car Plays: San Diego”), in elevators (Moxie Theatre’s “Counterweight”) and at nearby La Jolla Shores (“Seafoam Sleepwalk”), but at the UC San Diego power plant (“Cornerstone”), in the basement of a campus building (“A Willow Grows Aslant”), even roaming all over San Diego (“Kamchatka”).

It’s an alternative-theater explosion that began with a notion Christopher Ashley had when he arrived at the Playhouse as its new artistic director in 2007.

A WoW tip sheet

• The WoW Festival takes in a special edition of the Museum of Contemporary Art San Diego’s “TNT” event, a music and art mash-up, at 7 p.m. today. (MCASD and UC San Diego are festival partners.) Go to wowfestival.org for ticket info.

• A beer garden will be open on festival grounds throughout most of the event; there also will be food trucks and free live music, including a Saturday performance by Sara Watkins of the Grammy-winning Nickel Creek.

• The Playhouse is making shuttle buses available for off-site performances; check with the theater for details.

• A number of shows are virtually sold out due to limited capacity, so be sure to check on tickets ahead of time.

• DonorNation is hosting drawings to award $500 cash to each of four winners at the fest; $500 also will be donated to the San Diego school of each winner’s choice. Go to donornation.org for details.

At the time, the James Irvine Foundation, now a major WoW supporter (along with the National Endowment for the Arts, the county of San Diego and DonorNation), was looking to make grants for theater innovation.

“(So we) went to Irvine and said site-specific theater is really a growth thing that’s going to be huge in American theater,” says Ashley.

The theater then set out to prove it by launching “Without Walls” with a series of one-off productions in locations from botanic gardens to martini bars.

Now, with the festival’s debut, “I think the Playhouse is really enjoying being in the right place at the right time,” Ashley says. “It feels as if (we’re) really cresting the wave of this kind of programming in modern theater.”

Almost literally, in the case of “Seafoam Sleepwalk,” the beach-based piece by master puppeteer Basil Twist. Here, a closer look at that and a few other works that should prove highlights of the festival:

• “100% San Diego”: The German theater troupe Rimini Protokoll has been busy recruiting San Diegans over the past few weeks and months to be part of this sprawling, reality-based piece. The idea is to distill the precise demographic makeup of our county down to a group of 100 residents.

Performances of the piece will involve some improv and surprises, as the creators have the “actors” answer questions and move about according to their responses. (The piece is the rare WoW event that actually takes final form inside a theater — the Playhouse’s Mandell Weiss Forum.)

The work, Rimini Protokoll says, may “tell the truth of modern San Diego life in a way graphs or pie charts never could.”

• “Platonov, or The Disinherited”: MIT professor and multimedia-theater pioneer Jay Scheib created this cinematic adaptation of a lesser-known work by Anton Chekhov (a play, in fact, whose manuscript Chekhov tried to burn).

The show takes place inside a custom-built one-bedroom house at UC San Diego’s “Stonehenge” sculpture garden, with a small schoolhouse and bar (yes, bar) next door. Towering overhead is a 35-foot drive-in movie screen; the audience watches from bleachers, the grass or cafe tables. All the action is filmed from inside the house, with Scheib himself operating the main camera.

The action focuses on an unhappily married protagonist living in a society that’s “teetering on the edge of foreclosure,” Scheib says.

“It being Chekhov, there’s a lot of humor. But it’s humor with really sharp teeth sometimes.”

• “We Built This City”: Anchoring the festival’s family events is this project by the Australian group Polyglot. The whole purpose of the piece — a construction site made up of thousands of cardboard boxes — is to build structures with the full intention of trampling, pummeling and otherwise tearing them down.

On Saturday, “City” is joined by free, artist-led workshops under the umbrella of Mass Creativity Day; the Playhouse is teaming with The New Children’s Museum for those happenings.

• “Seafoam Sleepwalk”: Twist masterminded the puppet designs for last year’s hi-tech musical “Yoshimi Battles the Pink Robots,” one of several Playhouse projects he has worked on. Now he unveils this ambitious piece, which involves a huge figure emerging from the waves at La Jolla Shores.

Twist says the work’s inspiration was the Greek goddess Aphrodite, “who was born from the sea foam — that’s actually what her name means, ‘sea foam.’ That’s kind of the thematic core of the piece.”

He notes it’ll take a crew of 11 (all clad in wetsuits) to make the action happen. (Needless to say, “it’s very physical, what we’re doing,” Twist acknowledges.)

The crew members — four from New York, seven from San Diego — are staying in a nearby beach house as they bring the concept into reality. A musician who worked on Twist’s earlier piece “Dogugaeshi” will perform on the beach as the figure emerges.

The free event is not only for those in the know, Twist adds, but “also for the general public, who may not be expecting it at all. We’re just gathering to watch a sort of happening.”

• “The Car Plays: San Diego”: Staged to major success as a stand-alone WoW production last year, this work returns in a new incarnation. The show, conceived by the L.A.-based Moving Arts, consists of 10-minute playlets that take place inside actual cars.

This time around, it includes works written by renowned actress-playwright Charlayne Woodard and Obie winner Kirsten Greenidge; the Playhouse’s Ashley himself will direct one play.